Exploration And Properties Of New Oxynitride Silicate Fluorescent Materials

Due to its many advantages such as high energy efficiency,environmental protection,and long service life,light emitting diodes(LEDs)have replaced traditional incandescent lamps and fluorescent lamps as a new generation of mainstream solid-state lighting sources.Although the current luminous efficiency of power white LEDs has exceeded 200 lm/W,to truly replace other high-power light sources and meet the needs of various lighting and display,the luminous efficiency of white LEDs needs to be further improved.Because high power and high brightness will cause significant thermal effects of LED devices,resulting in a decrease in luminous efficiency,improving the luminous performance of LED devices at high temperatures has become a current research focus of LED fluorescent materials.In this thesis,through material design and synthesis,the research on the thermal quenching performance of rare earth ion doped oxynitride silicate system luminescent materials is carried out.Through O/N ion doping and the synthesis of new compounds,an attempt is made to find an excellent thermal quenching performance.A new type of LED oxynitride luminescent material.In this paper,Ba-SiN and La-Ba-Mg-Si-O-N systems are selected as the research objects,and several oxynitride silicates are synthesized by high temperature solid phase method.The structure of the new compound was characterized by X-ray diffraction,electron diffraction,neutron diffraction,solid-state nuclear magnetic resonance,and other methods.At the same time,the luminescence properties such as Eu2+ doping thermal quenching performance were studied.The main work of this paper is as follows:(1)The BaSiN2:xEu2+(0.005?x?0.09)phosphor series was synthesized by the high-temperature solid-phase method.BaSiN2:0.03Eu2+with the best luminous intensity has a broad orange-yellow emission peak at 600 nm with a bandwidth of 117 nm.The photoluminescence(PL)characteristics,PL thermal stability,and fluorescence decay curve of the sample were studied to characterize the obtained sample.The selected BaSiN2:0.01Eu2+phosphor has strong resistance to thermal quenching,and its brightness at 700K maintained 95%of room temperature brightness.The quenching concentration of Eu2+in BaSiN2 is about 0.03,which is attributed to the dipole-quadrupole interaction.The results show that BaSiN2:Eu2+ phosphor can be used as a potential application for high-temperature and high-power pc-LEDs.A new type of oxynitride silicate Ba3.3La7Li0.3Mg2.5Si13N26.3O6.7(BLLMSNO)was synthesized by the air pressure sintering method.The crystal structure was determined by X-ray single crystal diffraction analysis.Ba3.3La7Li0.3Mg2.5Si13N26.3O6.7 belongs to the hexagonal crystal system,the space group is P-6m2(no.187),and the unit cell parameter is a=b=16.8099(3)(?),c=9.73623(19)A.The SiN4 tetrahedron and the twisted LaN5 quadrangular pyramid form the three-dimensional framework of the crystal structure through common vertex connection and common edge connection.La3+ is located in the four-membered ring channel of the skeleton to compensate for the structural charge.Under the excitation of 465 nm blue light,Ba3.3La7Li0.3Mg2.5Si13N26.3O6.7:Eu2+phosphor exhibits red light emission,the maximum emission wavelength is at 650 nm,and the halfwidth of the emission spectrum is 95 nm.The luminous intensity of this new type of nitride phosphor at 450 K is about 40%of that at room temperature,which may be related to the smaller bandgap of the phosphor matrix.The phosphor has good thermal stability and water stability.After being soaked in water for 20 days,the luminous intensity still reaches more than 90%of the unsoaked intensity.The X-ray powder diffraction of the sample at 700? has no other peaks.The thermal stability of Ba3.3La7Li0.3Mg2.5Si13N26.3O6.7:Eu2+red phosphor has the potential to be applied to white LEDs in humid environments.